How to create a foreign key - for referential integrity - in the foreign keys tab using the Add button

How do you create a foreign key in the foreign keys tab? There is an Add button there, but I don't know how to use it.

My tables use Innodb. The particular table in question has two columns. They both contain integers that are identical to the primary keys in two other tables. So referential integrity is established, but I want to enforce it.

Does anyone know the exact procedure for using the Add button in the foreign keys tab to create foreign keys? Can I apply foreign keys to the existing columns?

Just set values in all fields:
- click "add"
- give it a name or use the default one ("FK1")
- select column name(s) in current table
- select reference table
- select columns from reference table
- set the "on update" and "on delete" behaviour

Thank you for your advice. I followed your instructions, but after "select column name in current table" Heidi asks me to save the table, and when doing so, I get an error message 1064. It is something like "right syntax to use near ') REFERENCES' '()'". I can't tell exactly what the error message is because the font is small, and I cannot select it with my mouse to paste it in a larger font.

Is there a bug in the software? Do you have any idea what the problem might be?

Okay, I didn't know you could do that. Here's the error:
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Error
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SQL Error (1064): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') REFERENCES `` ()' at line 2
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OK
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1. I clicked on a table in the left pane, then selected the Table tab and the Foreign Keys tab.
2. I clicked the green Add button.
3. I clicked to the left of column 6, which contains integers only. This turns the column blue (a horizontal blue bar).
4. I clicked the table containing the foreign key, and a Save Modified Table requester box appears.
5. I clicked Yes in the requester to save, and I get the error. The modified version of the table is not saved.